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Long-lived
Terms modified by Long-lived Selected AbstractsTwo Halogeno(cyano)cuprates with Long-Lived and Strong Luminescence.CHEMINFORM, Issue 36 2005Xi Liu Abstract For Abstract see ChemInform Abstract in Full Text. [source] Complex chromosome aberrations persist in individuals many years after occupational exposure to densely ionizing radiation: An mFISH studyGENES, CHROMOSOMES AND CANCER, Issue 1 2005M. Prakash Hande Long-lived, sensitive, and specific biomarkers of particular mutagenic agents are much sought after and potentially have broad applications in the fields of cancer biology, epidemiology, and prevention. Many clastogens induce a spectrum of chromosome aberrations, and some of them can be exploited as biomarkers of exposure. Densely ionizing radiation, for example, alpha particle radiation (from radon or plutonium) and neutron radiation, preferentially induces complex chromosome aberrations, which can be detected by the 24-color multifluor fluorescence in situ hybridization (mFISH) technique. We report the detection and quantification of stable complex chromosome aberrations in lymphocytes of healthy former nuclear-weapons workers, who were exposed many years ago to plutonium, gamma rays, or both, at the Mayak weapons complex in Russia. We analyzed peripheral-blood lymphocytes from these individuals for the presence of persistent complex chromosome aberrations. A significantly elevated frequency of complex chromosome translocations was detected in the highly exposed plutonium workers but not in the group exposed only to high doses of gamma radiation. No such differences were found for simple chromosomal aberrations. The results suggest that stable complex chromosomal translocations represent a long-lived, quantitative, low-background biomarker of densely ionizing radiation for human populations exposed many years ago. © 2005 Wiley-Liss, Inc. [source] Long-lived layered silicates-immobilized 2,6-bis(imino)pyridyl iron (II) catalysts for hybrid polyethylene nanocomposites by in situ polymerization: Effect of aryl ligand and silicate modificationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2009Giuseppe Leone Abstract Heterogeneous-layered silicate-immobilized 2,6-bis(imino)pyridyl iron (II) dichloride/MMAO catalysts, in which the active polymerization species are intercalated within sodium- and organomodified-layered silicate galleries, were prepared for producing hybrid exfoliated polyethylene (PE) nanocomposites by means of in situ polymerization. The inorganic filler was first treated with modified-methylaluminoxane (MMAO) to produce a supported cocatalyst: MMAO reacts with silicates replacing most of the organic surfactant, thus modifying the original crystallographic clay order. MMAO anchored to the nanoclay was able to activate polymerization iron complexes initiating the polymer growth directly from the filler lamellae interlayer. The polymerization mechanism taking place in between the montmorillonite lamellae separates the layers, thus promoting deagglomeration and effective clay dispersion. Transmission electron microscopy revealed that in situ polymerization by catalytically active iron complexes intercalated within the lower organomodified clay led to fine dispersion and high exfoliation extent. The intercalated clay catalysts displayed a longer polymerization life-time and brought about ethylene polymerization more efficiently than analogous homogeneous systems. PEs having higher molecular masses were obtained. These benefits resulted to be dependent more on the filler nature than on the ligand environment around the iron metal center and the experimental synthetic route. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 548,564, 2009 [source] Testing the intermediate disturbance hypothesis: when will there be two peaks of diversity?DIVERSITY AND DISTRIBUTIONS, Issue 1 2005Karin Johst ABSTRACT Succession after disturbances generates a mosaic of patches in different successional stages. The intermediate disturbance hypothesis predicts that intermediate disturbances lead to the highest diversity of these stages on a regional scale resulting in a hump-shaped diversity,disturbance curve. We tested this prediction using field data of forest succession and hypothetical succession scenarios in combination with analytical and simulation models. According to our study the main factors shaping the diversity,disturbance curve and the position of the diversity maximum were the transition times between the successional stages, the transition type, neighbourhood effects and the choice of diversity measure. Although many scenarios confirmed the intermediate disturbance hypothesis we found that deviations in the form of two diversity maximums were possible. Such bimodal diversity,disturbance curves occurred when early and late successional stages were separated by one or more long-lived (compared to the early stages) intermediate successional stages. Although the field data which met these conditions among all those tested were rare (one of six), the consequences of detecting two peaks are fundamental. The impact of disturbances on biodiversity can be complex and deviate from a hump-shaped curve. [source] Defining the OE hearg: a preliminary archaeological and topographic examination of hearg place names and their hinterlandsEARLY MEDIEVAL EUROPE, Issue 4 2007Sarah Semple The OE term hearg is interpreted variously as ,pagan temple', ,hilltop sanctuary' and even ,idol'. It is a rare survival in the English place-name record. When it can be identified, the place name is commonly considered to refer to a location of pre-Christian religious activity, specifically a pagan Anglo-Saxon temple. Taking inspiration from the extensive and methodologically well-advanced studies in Scandinavia, which have successfully related place-name evidence for cultic and religious sites with the archaeology and topography of these localities, this paper adopts and uses a similar methodology to investigate the archaeological and topographic character of a selection of hearg locations. The traditional interpretations of the place name are questioned and evidence is presented that these sites are characterized by long-lived, localized cult practice spanning the late prehistoric to early historic periods, but with activity reaching a zenith in the late Iron Age to Romano-British eras, rather than the fifth to seventh centuries AD. [source] Keeping the herds healthy and alert: implications of predator control for infectious diseaseECOLOGY LETTERS, Issue 9 2003Craig Packer Abstract Predator control programmes are generally implemented in an attempt to increase prey population sizes. However, predator removal could prove harmful to prey populations that are regulated primarily by parasitic infections rather than by predation. We develop models for microparasitic and macroparasitic infection that specify the conditions where predator removal will (a) increase the incidence of parasitic infection, (b) reduce the number of healthy individuals in the prey population and (c) decrease the overall size of the prey population. In general, predator removal is more likely to be harmful when the parasite is highly virulent, macroparasites are highly aggregated in their prey, hosts are long-lived and the predators select infected prey. [source] Estimating the Fractional Order of Integration of Yields in the Brazilian Fixed Income MarketECONOMIC NOTES, Issue 3 2007Benjamin M. Tabak This paper presents evidence that yields on the Brazilian fixed income market are fractionally integrated, and compares the period before and after the implementation of the Inflation Targeting (IT) regime. The paper employs the commonly used GPH estimator and recently developed wavelets-based estimator of long memory. Empirical results suggest that interest rates are fractionally integrated and that interest rate spreads are fractionally integrated, with a higher order of integration in the period after the implementation of the IT regime. These results have important implications for the development of macroeconomic models for the Brazilian economy and for long-term forecasting. Furthermore, they imply that shocks to interest rates are long-lived. [source] Feasibility of conducting the micronucleus test in circulating erythrocytes from different mammalian species: An anatomical perspectiveENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 9 2006Ion Udroiu Abstract The in vivo mammalian micronucleus test can be conducted easily on peripheral blood samples since the maturation of erythrocytes involves the loss of the major nucleus. In addition, mature erythrocytes are relatively long-lived, so that the test potentially can detect genotoxic damage caused by chronic exposures. However, some species have spleens that remove micronuclei from the peripheral circulation, making such measurements problematical. This report summarises haematological and mutagenesis studies dealing with this subject and provides an anatomical interpretation of the phenomenon. Anatomical features can be used to identify those species in which micronuclei are removed by the spleen. Environ. Mol. Mutagen., 2006. © 2006 Wiley-Liss, Inc. [source] Kleptoplasty in an Antarctic dinoflagellate: caught in evolutionary transition?ENVIRONMENTAL MICROBIOLOGY, Issue 1 2007Rebecca J. Gast Summary Photosynthetic dinoflagellates contain a diverse collection of plastid types, a situation believed to have arisen from multiple endosymbiotic events. In addition, a number of heterotrophic (phagotrophic) dinoflagellates possess the ability to acquire chloroplasts temporarily by engulfing algae and retaining their chloroplasts in a functional state. These latter relationships typically last from a few days to weeks, at which point the chloroplasts lose function, are digested and replaced with newly acquired plastids. A novel and abundant dinoflagellate related to the icthyotoxic genera Karenia and Karlodinium was recently discovered by us in the Ross Sea, Antarctica. Sequencing of its plastid small subunit ribosomal gene indicated that it did not share evolutionary history with the plastids of Karenia or Karlodinium, but was closely related to the free-living haptophyte Phaeocystis antarctica, a species that often dominates phytoplankton blooms in the Ross Sea. Chloroplast uptake was observed to occur rapidly (within 2 days), with retention in cultures being long-lived (several months) but not permanent. The dinoflagellate was also incapable of growing indefinitely in continuous darkness with algae as prey. Our findings may indicate an emerging endosymbiotic event yielding a dinoflagellate that is presently neither purely phototrophic nor purely heterotrophic, but occupies a niche juxtaposed between these contrasting nutritional modes. [source] Multicomponent Supramolecular Devices: Synthesis, Optical, and Electronic Properties of Bridged Bis-dirhodium and -diruthenium Complexes,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Anne Petitjean Abstract Four ruthenium- and rhodium-based metal,metal-bonded multicomponent systems have been synthesized, and their absorption, redox, spectroelectrochemical and structural properties have been studied. The absorption spectra of the four bis-dimetallic compounds M2LM2, where L is a bridging ligand and M is rhodium or ruthenium, exhibit very strong bands in the UV, visible and, for the diruthenium species, near-IR region. The low-energy absorption bands are assigned to charge-transfer transitions involving a metal,metal bonding orbital as the donor and an orbital centered on the bis-tetradentate aromatic ligands as the acceptor (metal,metal to ligand charge transfer, M2LCT). Each compound exhibits reversible bridging-ligand-centered reductions at mild potentials and several reversible oxidation processes. The oxidation signals of the two equivalent dimetallic centers of each bis-dimetallic compound are split, with the splitting , a measure of the electronic coupling , depending on both the metal and bridging ligand. The mixed-valence species of the dirhodium species was investigated, and the electronic coupling matrix element calculated from the experimental intervalence band parameters for one of them (86 cm,1) indicates a significant inter-component electronic interaction which compares well with good electron conducting anionic bridges such as cyanides. Although none of these compounds is luminescent, the M2LCT excited state of one of the bis-dirhodium complexes is relatively long-lived (about 6 ,s) in degassed acetonitrile at room temperature. The results presented here are promising for the development of linear poly-dimetallic complexes built on longer naphthyridine-based strands, with significant long-range electronic coupling and molecular-wire-like behavior. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A guide to practical babooning: Historical, social, and cognitive contingencyEVOLUTIONARY ANTHROPOLOGY, Issue 3 2009Louise Barrett Professor of Psychology at the University of Lethbridge Abstract As ecologically adaptable animals, baboons are distributed widely across Africa, and display a variety of morphological and behavioral differences that reflect both local ecology and a complex evolutionary history. As long-lived, slowly reproducing animals, baboons face numerous ecological challenges to survival and successful reproduction. As group-living animals, the social world presents an equally diverse array of challenges that require the negotiation of individual needs within the constraints imposed by others. Understanding how all these facets of baboon evolutionary history, life history, ecology, sociality, and cognition fit together is an enormous but engaging challenge, and despite one hundred years of study, it is clear there is a still much to learn about the various natural histories of baboons. What also is clear, however, is that an appreciation of contingency holds the key to understanding all these facets of baboon evolution and behavior. In what follows, I hope to illustrate exactly what I mean by this, highlighting along the way that history is not to be ignored, variability is information and not merely "noise", and that behavioral and cognitive complexity can be two very different things. [source] ORIGINAL ARTICLE: Implications of fisheries-induced evolution for stock rebuilding and recoveryEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2009Katja Enberg Abstract Worldwide depletion of fish stocks has led fisheries managers to become increasingly concerned about rebuilding and recovery planning. To succeed, factors affecting recovery dynamics need to be understood, including the role of fisheries-induced evolution. Here we investigate a stock's response to fishing followed by a harvest moratorium by analyzing an individual-based evolutionary model parameterized for Atlantic cod Gadus morhua from its northern range, representative of long-lived, late-maturing species. The model allows evolution of life-history processes including maturation, reproduction, and growth. It also incorporates environmental variability, phenotypic plasticity, and density-dependent feedbacks. Fisheries-induced evolution affects recovery in several ways. The first decades of recovery were dominated by demographic and density-dependent processes. Biomass rebuilding was only lightly influenced by fisheries-induced evolution, whereas other stock characteristics such as maturation age, spawning stock biomass, and recruitment were substantially affected, recovering to new demographic equilibria below their preharvest levels. This is because genetic traits took thousands of years to evolve back to preharvest levels, indicating that natural selection driving recovery of these traits is weaker than fisheries-induced selection was. Our results strengthen the case for proactive management of fisheries-induced evolution, as the restoration of genetic traits altered by fishing is slow and may even be impractical. [source] Voracious invader or benign feline?FISH AND FISHERIES, Issue 3 2009A review of the environmental biology of European catfish Silurus glanis in its native, introduced ranges Abstract A popular species for food and sport, the European catfish (Silurus glanis) is well-studied in its native range, but little studied in its introduced range. Silurus glanis is the largest-bodied freshwater fish of Europe and is historically known to take a wide range of food items including human remains. As a result of its piscivorous diet, S. glanis is assumed to be an invasive fish species presenting a risk to native species and ecosystems. To assess the potential risks of S. glanis introductions, published and ,grey' literature on the species' environmental biology (but not aquaculture) was extensively reviewed. Silurus glanis appears well adapted to, and sufficiently robust for, translocation and introduction outside its native range. A nest-guarding species, S. glanis is long-lived, rather sedentary and produces relatively fewer eggs per body mass than many fish species. It appears to establish relatively easily, although more so in warmer (i.e. Mediterranean) than in northern countries (e.g. Belgium, UK). Telemetry data suggest that dispersal is linked to flooding/spates and human translation of the species. Potential impacts in its introduced European range include disease transmission, hybridization (in Greece with native endemic Aristotle's catfish [Silurus aristotelis]), predation on native species and possibly the modification of food web structure in some regions. However, S. glanis has also been reported (France, Spain, Turkmenistan) to prey intensively on other non-native species and in its native Germany to be a poor biomanipulation tool for top-down predation of zooplanktivorous fishes. As such, S. glanis is unlikely to exert trophic pressure on native fishes except in circumstances where other human impacts are already in force. In summary, virtually all aspects of the environmental biology of introduced S. glanis require further study to determine the potential risks of its introduction to novel environments. [source] Complex chromosome aberrations persist in individuals many years after occupational exposure to densely ionizing radiation: An mFISH studyGENES, CHROMOSOMES AND CANCER, Issue 1 2005M. Prakash Hande Long-lived, sensitive, and specific biomarkers of particular mutagenic agents are much sought after and potentially have broad applications in the fields of cancer biology, epidemiology, and prevention. Many clastogens induce a spectrum of chromosome aberrations, and some of them can be exploited as biomarkers of exposure. Densely ionizing radiation, for example, alpha particle radiation (from radon or plutonium) and neutron radiation, preferentially induces complex chromosome aberrations, which can be detected by the 24-color multifluor fluorescence in situ hybridization (mFISH) technique. We report the detection and quantification of stable complex chromosome aberrations in lymphocytes of healthy former nuclear-weapons workers, who were exposed many years ago to plutonium, gamma rays, or both, at the Mayak weapons complex in Russia. We analyzed peripheral-blood lymphocytes from these individuals for the presence of persistent complex chromosome aberrations. A significantly elevated frequency of complex chromosome translocations was detected in the highly exposed plutonium workers but not in the group exposed only to high doses of gamma radiation. No such differences were found for simple chromosomal aberrations. The results suggest that stable complex chromosomal translocations represent a long-lived, quantitative, low-background biomarker of densely ionizing radiation for human populations exposed many years ago. © 2005 Wiley-Liss, Inc. [source] Deformation history of the eclogite- and jadeitite-bearing mélange from North Motagua Fault Zone, Guatemala: insights in the processes of a fossil subduction channelGEOLOGICAL JOURNAL, Issue 2 2009Michele Marroni Abstract In Guatemala, along the northern side of the Motagua Valley, a mélange consisting of blocks of eclogite and jadeitite set in a metaserpentinitic and metasedimentary matrix crops out. The metasedimentary rocks display a complex deformation history that includes four tectonic phases, from D1 to D4. The D1 phase occurs only as a relic and is characterized by a mineral assemblage developed under pressure temperature (P,T) conditions of 1.00,1.25,GPa and 206,263°C. The D2 phase, characterized by isoclinal folds, schistosity and mineral/stretching lineation, developed at P,T conditions of 0.70,1.20,GPa and 279,409°C. The following D3 and D4 phases show deformations developed at shallower structural levels. Whereas the D1 phase can be interpreted as the result of underplating of slices of oceanic lithosphere during an intraoceanic subduction, the following phases have been acquired by the mélange during its progressive exhumation through different mechanisms. The deformations related to the D2 and D3 phases can be regarded as acquired by extrusion of the mélange within a subduction channel during a stage of oblique subduction. In addition, the structural evidences indicate that the coupling and mixing of different blocks occurred during the D2 phase, as a result of flow reverse and upward trajectory in the subduction channel. By contrast, the D4 phase can be interpreted as related to extension at shallow structural levels. In this framework, the exhumation-related structures in the mélange indicate that this process, probably long-lived, developed through different mechanisms, active in the subduction channel through time. Copyright © 2009 John Wiley & Sons, Ltd. [source] Postfire response of North American boreal forest net primary productivity analyzed with satellite observationsGLOBAL CHANGE BIOLOGY, Issue 8 2003Jeffrey A. Hicke Abstract Fire is a major disturbance in the boreal forest, and has been shown to release significant amounts of carbon (C) to the atmosphere through combustion. However, less is known about the effects on ecosystems following fire, which include reduced productivity and changes in decomposition in the decade immediately following the disturbance. In this study, we assessed the impact of fire on net primary productivity (NPP) in the North American boreal forest using a 17-year record of satellite NDVI observations at 8- km spatial resolution together with a light-use efficiency model. We identified 61 fire scars in the satellite observations using digitized fire burn perimeters from a database of large fires. We studied the postfire response of NPP by analyzing the most impacted pixel within each burned area. NPP decreased in the year following the fire by 60,260 g C m,2 yr,1 (30,80%). By comparing pre- and postfire observations, we estimated a mean NPP recovery period for boreal forests of about 9 years, with substantial variability among fires. We incorporated this behavior into a carbon cycle model simulation to demonstrate these effects on net ecosystem production. The disturbance resulted in a release of C to the atmosphere during the first 8 years, followed by a small, but long-lived, sink lasting 150 years. Postfire net emissions were three times as large as from a model run without changing NPP. However, only small differences in the C cycle occurred between runs after 8 years due to the rapid recovery of NPP. We conclude by discussing the effects of fire on the long-term continental trends in satellite NDVI observed across boreal North America during the 1980s and 1990s. [source] Strong Ultra-Broadband Near-Infrared Photoluminescence from Bismuth-Embedded Zeolites and Their DerivativesADVANCED MATERIALS, Issue 36 2009Hong-Tao Sun Zeolites with embedded bismuth compounds display strong, air-stable, long-lived, ultrabroadband, and tunable near-infrared photoluminescence (see picture). Bismuth ions not only act as luminescence-active centers, but also as blocks for selectively closing the "in,out windows" of water molecules. Bismuth active centers can be sealed in a low-vibrational environment by bismuth agglomerates even when the sample still contains a large amount of water. [source] Heterogeneous grazing causes local extinction of edible perennial shrubs: a matrix analysisJOURNAL OF APPLIED ECOLOGY, Issue 2 2001L.P. Hunt Summary 1Population modelling and field measurements of births, growth and deaths were used to investigate the long-term change in abundance of Atriplex vesicaria (Chenopodiaceae), a long-lived, palatable, perennial shrub, under sheep grazing. Of particular interest was whether A. vesicaria is at risk of being eliminated throughout grazed paddocks when the recommended practice of continuous grazing at conservative stocking rates is employed. 2Time-invariant matrix population models indicated that the A. vesicaria population was in decline over much of the study paddock, but the rate of decline was greatest nearer to the water point (population growth rate , , 0·8). Time-varying stochastic matrix models projected that the A. vesicaria population would become locally extinct at most sites up to approximately 2200 m from water, occurring first closer to water (within 12,29 years). The population was stable (i.e. , , 1) at sites greater than 2200 m from water over the projection period of 100 years. 3Decreases in adult survival and recruitment made the largest contributions to reductions in the population growth rate. However, there were spatial patterns centred on the water point in the degree to which particular demographic processes contributed to these reductions, because of a grazing gradient and the differential sensitivity of demographic processes to grazing. Thus decreases in recruitment contributed to reductions in the population growth rate at greater distances. Such responses, together with the sensitivity of the population growth rate to these processes, determined the spatial pattern in population growth. 4The results suggest that piospheres (i.e. the zone of impact) continue to expand over many years under set-stocking so that the area around the water point that is devoid of A. vesicaria becomes larger. The process of expansion appears to first involve the inhibition of recruitment, followed by eventual mortality of established shrubs. 5The large contribution of adult survival to the population growth rate in A. vesicaria suggests that minimizing the mortality of established adults should be a priority for management. This is likely to involve resting from grazing at critical times such as during extended dry periods. This may also permit increased levels of recruitment during subsequent moister periods. [source] Insights from comparative analyses of aging in birds and mammalsAGING CELL, Issue 2 2010Robert E. Ricklefs Summary Many laboratory models used in aging research are inappropriate for understanding senescence in mammals, including humans, because of fundamental differences in life history, maintenance in artificial environments, and selection for early aging and high reproductive rate. Comparative studies of senescence in birds and mammals reveal a broad range in rates of aging among a variety of taxa with similar physiology and patterns of development. These comparisons suggest that senescence is a shared property of all vertebrates with determinate growth, that the rate of senescence has been modified by evolution in response to the potential life span allowed by extrinsic mortality factors, and that most variation among species in the rate of senescence is independent of commonly ascribed causes of aging, such as oxidative damage. Individuals of potentially long-lived species, particularly birds, appear to maintain high condition to near the end of life. Because most individuals in natural populations of such species die of aging-related causes, these populations likely harbor little genetic variation for mechanisms that could extend life further, or these mechanisms are very costly. This, and the apparent evolutionary conservatism in the rate of increase in mortality with age, suggests that variation in the rate of senescence reflects fundamental changes in organism structure, likely associated with the rate of development, rather than physiological or biochemical processes influenced by a few genes. Understanding these evolved differences between long-lived and short-lived organisms would seem to be an essential foundation for designing therapeutic interventions with respect to human aging and longevity. [source] The evolutionary ecology of vegetative dormancy in mature herbaceous perennial plantsJOURNAL OF ECOLOGY, Issue 5 2009Richard P. Shefferson Summary 1.,I present an evolutionary ecology interpretation of vegetative dormancy in mature herbaceous perennials. This kind of vegetative dormancy has been noted for at least 40 years, but has only recently become a topic of study. 2.,Vegetative dormancy may be considered in a life-history context. Both vegetative dormancy and mortality typically decrease with increasing size. Vegetative dormancy's relationship to reproduction is more complex, because some species increase flowering and fruiting after dormancy while others do the opposite. 3.,If vegetative dormancy is adaptive, then it is most likely a bet-hedging trait. Dormancy-prone plants are often long-lived, and in such organisms, bet-hedging traits should counter the effects of environmental stochasticity on adult survival. This adaptive context may vary by life span, because in shorter-lived plants, fitness is most sensitive to changes in reproduction rather than survival. 4.,Vegetative dormancy could evolve if the costs of sprouting ever outweigh the benefits. The benefits of sprouting include: (i) photosynthesis and (ii) the opportunity to flower and reproduce. The costs include: (i) greater chance of herbivory, (ii) greater need for limiting nutrients, and (iii) greater maintenance costs. The many losses of photosynthesis among plants suggest that these benefits may not always outweigh the costs. 5.,Vegetative dormancy may be an evolutionary step towards the loss of photosynthesis. Many non-photosynthetic plants acquire carbon from their mycorrhizal fungi. Many autotrophic, dormancy-prone plants also acquire some carbon from their mycorrhizal fungi. Further, non-photosynthetic plants often become dormant to an even greater extent than autotrophic, dormancy-prone plants. 6.Synthesis,Vegetative dormancy often occurs in clades with non-photosynthetic, myco-heterotrophic plants, with implications for the evolution of traits involved in carbon nutrition. The links between vegetative dormancy, other life-history traits, mycorrhizas and the loss of photosynthesis should provide exciting directions for further research in plant evolutionary ecology. Particularly needed is an assessment of the physiology of vegetative dormancy, including whether the mycorrhiza is a carbon source in all dormancy-prone plant species. Equally important is a better understanding of the genetic relationships among photosynthesis, myco-heterotrophy and dormancy. [source] Multigenerational analysis of spatial structure in the terrestrial, food-deceptive orchid Orchis masculaJOURNAL OF ECOLOGY, Issue 2 2009Hans Jacquemyn Summary 1In long-lived, terrestrial orchids, strong aggregation of adults and recruits within populations and pronounced spatial association between recruits and adults can be expected when seed dispersal is limited, probabilities of seed germination decrease with increasing distance from mother plants and/or not all mother plants contribute to future generations. When individuals are distributed evenly across life-history stages, these processes can also be expected to result in a significant fine-scale spatial genetic structure in recruits that will persist into the adult-stage class. 2We combined detailed spatial genetic and point pattern analyses across different generations with parentage analyses to elucidate the role of the diverse processes that might determine spatial structure in Orchis mascula. 3Analyses of spatial point patterns showed a significant association between adults and recruits and similar clustering patterns for both. Weak, but highly significant spatial genetic structure was observed in adults and recruits, but no significant differences were observed across life stages, indicating that the spatial genetic structure present in recruits persists into the adult stage. 4Parentage analyses highlighted relatively short seed dispersal distances (median offspring-recruitment distance: 1.55 and 1.70 m) and differential contribution of mother plants to future generations. 5Persistence of fine-scale spatial genetic structure from seedlings into the adult stage class is consistent with the life history of O. mascula, whereas relatively large dispersal distances of both pollen and seeds compared to the fine-scale clustering of adults and seedlings suggest overlapping seed shadows and mixing of genotypes within populations as the major factors explaining the observed weak spatial genetic structure. 6Nonetheless, comparison of the spatial association between recruits and adults with the genetic analysis of offspring-parent distances suggests that the tight clustering of recruits around adults was probably caused by decreasing probabilities of seed germination with increasing distance from mother plants. 7Synthesis. This study shows that the approach presented here, which combines spatial genetic and spatial pattern analyses with parentage analyses, may be broadly applied to other plant species to elucidate the processes that determine spatial structure within their populations. [source] The efficiency of mitochondrial electron transport chain is increased in the long-lived mrg19 Saccharomyces cerevisiaeAGING CELL, Issue 6 2009Nitish Mittal Summary Integrity of mitochondrial functionality is a key determinant of longevity in several organisms. In particular, reduced mitochondrial ROS (mtROS) production leading to decreased mtDNA damage is believed to be a crucial aspect of longevity. The generation of low mtROS was thought to be due to low mitochondrial oxygen consumption. However, recent studies have shown that higher mitochondrial oxygen consumption could still result in low mtROS and contribute to longevity. This increased mitochondrial efficiency (i.e. low mtROS generated despite high oxygen consumption) was explained as a result of mitochondrial biogenesis, which provides more entry points for the electrons to the electron transport chain (ETC), thereby resulting in low mtROS production. In this study, we provide evidence for the existence of an alternative pathway to explain the observed higher mitochondrial efficiency in the long-lived mrg19 mutant of Saccharomyces cerevisiae. Although we observe similar amounts of mitochondria in mrg19 and wild-type (wt) yeast, we find that mrg19 mitochondria have higher expression of ETC components per mitochondria in comparison with the wt. These findings demonstrate that more efficient mitochondria because of increased ETC per mitochondria can also produce less mtROS. Taken together, our findings provide evidence for an alternative explanation for the involvement of higher mitochondrial activity in prolonging lifespan. We anticipate that similar mechanisms might also exist in eukaryotes including human. [source] Contrasting effects of grazing and hay cutting on the spatial and genetic population structure of Veratrum album, an unpalatable, long-lived, clonal plant speciesJOURNAL OF ECOLOGY, Issue 2 2002David Kleijn Summary 1 ,Vegetation change induced by large herbivores is driven by the effects of grazers on populations of individual plant species. Short-term experimental or demographic studies may be insufficient when investigating the population responses of long-lived clonal plant species. 2 ,We therefore examined the effects of grazing on such a plant (Veratrum album) by comparing the spatial and genetic structure of populations in grasslands subject to long-term grazing or mowing for hay. 3 , V. album is a locally dominant species that is avoided by large herbivores due to its toxicity. RAPD-phenotypes of a subsample of c. 50 shoots, and co-ordinates and dry weight of all shoots, were determined in a 5 × 10 m plot in each of four meadow and four pasture populations. 4 ,The breeding system of the genus Veratrum was previously unknown but our experimental finding that cross-pollinated but not self-pollinated or unpollinated flowers produced as many seeds as freely pollinated flowers suggested that V. album is a predominantly cross-pollinating species. 5 ,Both the spatial and genetic population structure differed markedly between the two grassland types. Clonal expansion of established plants in pastures led to populations consisting of larger shoots that were significantly more aggregated at a small spatial scale. Populations also had a higher proportion of flowering shoots, less seedling recruitment and a lower genotypic diversity in pastures than hay meadows. 6 ,The differences in population structure appear to be due to hay meadow populations reproducing primarily by seeds, whereas clonal reproduction accounts for half of the population growth in pastures. We suggest that, as livestock selectively avoids V. album shoots, grazing indirectly promotes plant growth, which results in an enhanced vegetative reproduction as well as a higher seed production. Experimental studies are, however, needed to determine why and how grazing adversely affects seedling recruitment. 7 ,Detailed information on population level responses of unpalatable dominant plant species, such as provided by the present study, may help us understand and predict vegetation change in response to changing levels of herbivory. [source] The demography of slow aging in male and female Drosophila mutant for the insulin-receptor substrate homologue chicoAGING CELL, Issue 1 2002Meng-Ping Tu Summary Hypomorphic mutants affecting the Drosophila insulin/IGF signal pathway are reported to increase longevity in females but not in males. To understand this sex-difference, we conducted a large-scale demographic study with three new isogenic strains of alleles at chico, the insulin-receptor substrate homologue. We verify that female dwarf homozygotes (ch1/ch1) and normal-sized heterozygotes (ch1/+) are long-lived, as originally reported. We find for the first time that male heterozygotes are long-lived relative to wildtype, by about 50%. The life span of male ch1/ch1 is similar to that of wildtype but these dwarf males age at a slow demographic rate. The levels of demographic frailty and of age-independent mortality are elevated in ch1/ch1 males, counteracting the effect of slow aging upon life expectancy. Mortality deceleration occurs amongst the oldest-old wildtype adults, as seen in many organisms. Remarkably, in similarly sized cohorts of male and female ch1/ch1 and of male ch1/+ mortality deceleration is absent. Mortality deceleration is a phenotype of chico. [source] Growth and reproductive biology of the foxfish Bodianus frenchii, a very long-lived and monandric protogynous hermaphroditic labridJOURNAL OF FISH BIOLOGY, Issue 3 2010S. Cossington Samples of the foxfish Bodianus frenchii, collected over reefs on the lower west and south coasts of Western Australia, contained individuals ranging up to 78 years old. Although B. frenchii is far smaller than many other species within the Labridae, its maximum age is the greatest yet recorded for this highly speciose family and, together with Achoerodus gouldii, provides an example of a temperate hypsigenyine with exceptional longevity. Length and age compositions of females and males and the histological characteristics of gonads of a wide length range of individuals demonstrated that B. frenchii is a protogynous hermaphrodite. Furthermore, as, on both coasts, the length of the smallest male was greater than that at which all females had become mature, B. frenchii is a monandric protogynous hermaphrodite, i.e. all of its males are derived from functional females. Attainment of maturity by females is related more to length than age, whereas the reverse is true for sex change. On the basis of Schnute growth equations and length-to-body mass regression equations, the predicted length at age and body mass at length of fish on the south coast were greater than those on the west coast throughout life. Although B. frenchii spawns daily during the main spawning season, which extends from October to February on both coasts, its fecundity at any given length is substantially greater on the south than on the west coast. The more rapid growth of juveniles and earlier attainment of maturity by B. frenchii on the south coast than on the warmer west coast, together with maturation at a similar size on both coasts, run counter to the trends observed in many species and certain ecological theories regarding the relationships between life-cycle traits and latitude and temperature. The attainment by B. frenchii of a larger body length at age, of greater body mass at length and of greater fecundity at both length and body mass in fish on the south than on the west coast strongly suggests that conditions on the former, cooler coast are more favourable for this labrid, which belongs to a sub-genus whose other species typically live in cool, deep, temperate waters. [source] Temptations of weevil: feeding and ovipositional behaviour of Hylobius warreni Wood on host and nonhost bark in laboratory bioassaysAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2009Gareth R. Hopkins Abstract 1Warren root collar weevil Hylobius warreni Wood (Coleoptera: Curculionidae) is a long-lived, flightless insect native to coniferous forests across northern North America. Girdling by larval feeding causes significant mortality on young trees. The insect poses considerable challenges to reforestation. 2Adult weevils feed on all life stages of a variety of coniferous hosts prior to oviposition. Their relative feeding preferences, however, have not been quantified. Moreover, it is not known whether host bark influences oviposition behaviour. 3Feeding preferences of adult weevils were tested in both choice and no-choice laboratory bioassays using small branches from three conifers (lodgepole pine Pinus contorta var. latifolia, interior hybrid spruce Picea glauca×engelmannii, and Douglas-fir Pseudotsuga menziesii) and one deciduous tree (trembling aspen Populus tremuloides). Measurements included the surface area of bark consumed, rate of consumption, the number of days of feeding, and, in the no-choice assay, the number of eggs oviposited. 4Bark consumption was greatest on pine and Douglas-fir, followed by spruce. Little to no feeding occurred on aspen. Consumption did not vary between male versus female insects for any of the feeding metrics quantified. 5The presence of aspen branches did not inhibit feeding on any of the other species in the choice bioassays. 6The number of eggs laid by female insects did not differ significantly among tree species in the no-choice assay. Eggs were laid indiscriminately in the presence of all four host types. 7Results and opportunities for future research are discussed in the context of formulating new integrated pest management strategies for this insect, which is increasingly important in the period of reforestation subsequent to the mountain pine beetle epidemic in western Canada. [source] Light-emitting diode flashlights as effective and inexpensive light sources for fluorescence microscopyJOURNAL OF MICROSCOPY, Issue 1 2009J.B. ROBERTSON Summary Light-emitting diodes (LEDs) are becoming more commonly used as light sources for fluorescence microscopy. We describe the adaptation of a commercially available light-emitting diode flashlight for use as a source for fluorescence excitation. This light source is long-lived, inexpensive and is effective for excitation in the range of 440,600 nm. [source] Kinetic analysis of the cross reaction between dithioester and alkoxyamine by a Monte Carlo simulation,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2007Yong Ao Abstract A model reaction of dithioester and alkoxyamine is proposed to probe the reversible addition,fragmentation chain transfer (RAFT) process. The kinetics of the model reaction is analyzed and compared with that of pure alkoxyamine homolysis with a Monte Carlo simulation. Although the pure alkoxyamine obeys the law of persistent radical effect, the model reaction results in higher concentration of the persistent radical during the main period of the reaction. However, for a very fast RAFT process or a very low addition rate constant, the time dependence of the persistent radical concentration is quite close to that of pure alkoxyamine. Furthermore, the cross termination between the intermediate and alkyl radicals causes a retardation effect for the model reaction when the intermediate is relatively long-lived. The Monte Carlo simulation indicates that it is feasible to measure the individual rate constants of the RAFT process, such as the rate constant of addition, with a large excess of alkoxyamine. In addition, the special feature of the system with different leaving groups in the alkoxyamine and dithioester is also discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 374,387, 2007 [source] Design and synthesis of multifunctional glycidyl ethers that undergo frontal polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2006James V. Crivello Abstract An investigation of the photoactivated cationic ring-opening frontal polymerizations of a series of alkyl glycidyl ethers has been carried out with the aid of a novel technique, optical pyrometry. With this technique, the effects of the monomer structure on the frontal behavior of these monomers have been examined. Upon irradiation with UV light, the photopolymerizations of many alkyl glycidyl ethers display a prolonged induction period at room temperature as the result of the formation of long-lived, relatively stable secondary oxonium ions. The input of only a small amount of thermal activation energy is required to induce the further reaction of these species with a consequent autoaccelerated exothermic ring-opening polymerization. Photoactivated frontal polymerizations have been observed for both mono- and polyfunctional alkyl glycidyl ether monomers. The ability of monomers to exhibit frontal behavior has been found to be related to their ability to stabilize the secondary oxonium ion intermediates through multiple hydrogen-bonding effects to the ether groups present in the molecule. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6435,6448, 2006 [source] Millennia-long tree-ring records from Tasmania and New Zealand: a basis for modelling climate variability and forcing, past, present and future,JOURNAL OF QUATERNARY SCIENCE, Issue 7 2006Edward R. Cook Abstract Progress in the development of millennia-long tree-ring chronologies from Australia and New Zealand is reviewed from the perspective of modelling long-term climate variability there. Three tree species have proved successful in this regard: Huon pine (Lagarostrobos franklinii) from Tasmania, silver pine (L. colensoi) from the South Island of New Zealand, and kauri (Agathis australis) from the North Island of New Zealand. Each of these species is very long-lived and produces abundant quantities of well-preserved wood for extending their tree-ring chronologies back several millennia into the past. The growth patterns on these chronologies strongly correlate with both local and regional warm-season temperature changes over significant areas of the Southern Hemisphere (especially Huon and silver pine) and to ENSO variability emanating from the equatorial Pacific region (especially kauri). In addition, there is evidence for significant, band-limited, multi-decadal and centennial timescale variability in the warm-season temperature reconstruction based on Huon pine tree rings that may be related to slowly varying changes in ocean circulation dynamics in the southern Indian Ocean. This suggests the possibility of long-term climate predictability there. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||